The conventional techniques used to measure energy of a laser beam typically utilize costly technologies such as pyroelectric based sensors. Pyroelectric based sensors rely on the ability of certain materials to generate a temporary voltage when they are heated or cooled. Such sensors are costly to manufacture and can easily command prices of around one thousand dollars per unit.
Prior art thermopiles are based on thermocouples in series which generate a voltage based on the amount of heating caused by absorption of the laser. However, the absorber must be in close contact with the thermopile, and damage to the absorbing surface from the impinging laser will also likely damage the underlying thermopile. Furthermore, replacing the absorbing surface and reintegrating that surface with the thermopile is not easy, so that repair of the sensor is costly.
Prior art pyroelectric detectors are based on the pyroelectric effect, where certain crystals change their voltage based on their temperature. These materials are also susceptible to damage and are also expensive, and the sensor element is not easily replaced.
U.S. Pat. No. 5,758,969 issued to Freyaldenhoven describes an instrument for measuring the energy of optical radiation, particularly laser radiation. The '969 device uses a plurality of radiation absorbing plate-like foraminous elements which are disposed in a tubular housing such that the radiation entering at one end of the housing is successively absorbed by the radiation absorbing elements which are heated thereby. A fan disposed at the other end of the housing moves cooling air through the housing and through the radiation absorbing elements whereby the air is heated. From the temperature increase of the cooling air which is measured by a temperature measuring element, the energy of the optical radiation entering the housing is determined. While the '969 patent issued to Freyaldenhoven has merit it is perhaps a somewhat cumbersome way of determining the energy in a laser beam.
Therefore, a more robust and faster method of measuring the energy in a laser beam is required.
While such technologies as described above have proved useful in measuring and characterizing pulsed laser beams there is a need for less costly sensors.